An exploded view of an external gear pump.

Gear pumps use the meshing of gears to pump fluid by displacement. They are one of the most common types of pumps for hydraulic fluid power applications. There are two main variations; external gear pumps which use two external spur gears, and internal gear pumps which use an external and an internal spur gear. Gear pumps are fixed displacement, meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or pump. Gear pump. ... Gear pump. ... Manual water pump in Košice-Ťahanovce, Slovakia An electric driven pump of water works nearby the Hengstey See, Germany 19th century Dutch diesel pump in Rijswijk, Netherlands Manual pump used to obtain water in Afghanistan This article is about the mechanical device. ... Hydraulically powered cylinders are visible on this excavator. ... Spur gears found on a piece of farm equipment. ... A motor is a device that converts energy into mechanical power, and is often synonymous with engine. ...

Theory of operation

As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displace the fluid. The mechanical clearances are small—on the order of a thousandth of an inch (micrometres). The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards. A subset of the phases of matter, fluids include liquids, gases, plasmas and, to some extent, plastic solids. ...

The rigid design of the gears and housing allow for very high pressures and the ability to pump highly viscous fluids. The pitch drop experiment at the University of Queensland. ...

Many variations exist, including; helical and herringbone gear sets (instead of spur gears), lobe shaped rotors similar to superchargers, and mechanical designs that allow the stacking of pumps. The most common variations are shown below (the drive gear is shown blue and the idler is shown purple). For other meanings, see supercharger (disambiguation) A supercharger (sometimes called a blower), a positive displacement or centrifugal pump, is a gas compressor used to pump air into the cylinders of an internal combustion engine. ...

External gear pump design for hydraulic power applications.

Internal gear pump design for automotive oil pumps.

Internal gear pump design for high viscosity fluids.

Image:Gear pump. ... Image:Gear pump. ... Hydraulically powered cylinders are visible on this excavator. ... Image:Gear pump 2. ... Image:Gear pump 2. ... A colorized automobile engine The internal combustion engine is a heat engine in which the burning of a fuel occurs in a confined space called a combustion chamber. ... Image:Gear pump 3. ... Image:Gear pump 3. ... The pitch drop experiment at the University of Queensland. ...

Suction and pressure ports need to interface where the gears mesh (shown as dim gray lines in the internal pump images). Some internal gear pumps have an additional, crescent shaped seal (shown above, right).

Pump formulas;

• Flow rate in US gal/min = Displacement X rpm/231 (displacement in in³/revolution)
• Power in hp = US gal/min X (lbf/in³)/1714

Applications

External gear pumps are the most common type of pump for hydraulic power applications. This is because of their simplicity, reliability, and very high power ratings. A typical 10 hp (7 kW) gear pump may fit into a 4 x 4 x 4 inch (100 by 100 by 100 mm) envelope, a fraction of the size of a comparable electric motor. Maximum operating pressures are between 1000 and 4000 lbf/in² (7 and 28 MPa). Many commercial models are designed to operate as either a motor or pump. Some designs add load sensing modifications.

Internal gear pumps perform better at lower speeds and with higher viscosity fluids than external gear pumps. Engine oil pumps are usually internal gear designs. A colorized automobile engine The internal combustion engine is a heat engine in which the burning of a fuel occurs in a confined space called a combustion chamber. ...

Industry standards exist for gear pump mounting flanges, drive shaft sizes and splines, and ports. The suction port will usually be larger than the pressure port to reduce the possibility of cavitation. Cavitating propeller model in a water tunnel experiment Cavitation is the phenomenon where small and largely empty cavities are generated in a fluid, which expand to large size and then rapidly collapse, producing a sharp sound. ...

See also

• Vane pump

A vane pump is a positive displacement pump that consists of vanes in a rotor rotating inside of a cavity. ...

External links

Wikimedia Commons has media related to:

Gear pump

• External gear pump description
• Internal gear pump description
• Commercial manufacturer (external gear pumps)
• Commercial manufacturer (internal gear pumps)
• Commercial manufacturer (internal gear pumps)
• Gear pump article